Illuminating spotlight projector and lighting installation with offset light source

ABSTRACT

The invention concerns an illuminating spotlight emitting a narrow beam. The spotlight has a highly concentrated light source and a concave reflector for emitting an illuminating beam in a specific direction, along an emitting axis. A converging lens is interposed between the source and the reflector and in a plane passing through a conical segment. The source is bordered laterally on the reflector side with a sector of the converging lens providing a virtual image of the source located beyond the emitting axis, on the side opposite that of the lens. The virtual image of the light source is formed at the focus of the conical segment locally defining the reflector.

The present invention relates to an illuminating spotlight emitting anarrow beam, comprising a highly concentrated light source and a concavereflector for emitting an illuminating beam in a given direction, alongan axis of emission.

The invention relates also to a lighting installation produced usingsuch a spotlight.

In order to control the distribution of the lighting in an area or moregenerally, at a site, it is in many cases valuable to have a beam ofvery precise angular definition. That means that the aperture angle ofthe beam must be very small.

In general, the beam is a luminous beam of rays that are in theoryparallel, which beam is obtained by a parabolic reflector whose focalpoint corresponds to the light source of the bulb and whose axis is theaxis of emission. Part of such a spotlight is shown in diagrammaticsection in FIG. 1.

However, the rays that are emitted do not form a totally parallel beambecause the light source is neither a point source nor a monochromaticsource.

Accordingly, only the beams that are emitted by the source located atthe focal point F and strike the reflector represented by the segment ofa parabola UP generating it are emitted in the form of relativelyparallel rays. All the rays contained within the cone of axis X′X and ofhalf-angle δo/2, of generating line FP passing the edge of thereflector, are emitted directly in the form of rays that are radial andnot parallel to the axis X′X.

In practice, such a reflector is formed by a portion of a paraboloid ofrevolution of axis X′X, of focal point F and defined by its parameter p,its forward opening radius R2 and its rearward opening radius R1 (therearward opening serves for the passage of the lamp). The flux usedincreases when the radius R2 increases, and it is considered to be atits maximum when the characteristics of the reflector are such that:

p={square root over (R₁*R₂/2)}

The angle γ of the captured flux is delimited by the contour UP of thereflector. The development of a more enveloping reflector would resultin excessive dimensions. It must also be noted that the lamps have largedimensions relative to the reflector, and the real focal pointnecessarily extends beyond the theoretical focal point, which is themain cause of the lack of parallelism mentioned above. The divergenceincreases with the dimensions of the source or vice versa, if the focaldistance diminishes and the diameter of the reflector diminishesrelative to that of the source. The positioning of a lens in front ofthe opening face of the reflector might be considered, but it wouldcorrect not only the direct flux but also the flux of parallel raysreflected by the reflector.

In conclusion, the correction provided by a lens positioned at the frontwould not be very effective.

Finally, it must be noted that the effective angle of emission of a beamis very much greater than the angle attributed to, a light sourceequipped with a reflector, such as, for example, halogen bulbs equippeddirectly with a reflector. That angle is defined as being the angle ofemission of 50% of the luminous flux, the remainder of the flux beingemitted in directions that are not contained within that cone ofemission. The definition of the angle of illumination appears in FIG.1A, which shows the separation graph of the luminous intensity as afunction of the angle relative to the axis X′X (FIG. 1) Thatdistribution is a bell curve, and the angle of the spotlight is theangle giving, by definition, the intensity greater than the half-averageIM/2 relative to the maximum intensity IM in the direction of the axis(α=o). The angle α attributed to the beam is thus obtained, in whichangle the flux should be the maximum.

In practice, that means that the beam is not very precise at all.

The object of the present invention is to develop a spotlight allowingthe emission of a beam that has a very small angle and that groupstogether almost all of the luminous flux emitted by the source.

To that end, the invention relates to a spotlight of the type definedabove, characterised by

a convergent lens positioned between the source and the reflector,

in a plane passing through the axis of emission,

the concave reflector formed by a conic section (ellipse or parabola),

the source is bordered laterally on the side of the reflector by asector of the convergent lens giving a virtual image of the source,which virtual image is situated beyond the axis of emission, on theother side from the lens,

the virtual image of the light source being formed at the focal point ofthe conic section locally defining the reflector.

In an advantageous manner, the reflector comprises a body of revolutionabout the axis of emission XX. According to the circumstances, the conicis a parabola whose axis is parallel to the axis of emission.

Thanks to the displacement of the light source by its virtual image, itis possible to have a sector of a parabola of relatively large focaldistance, that is to say a highly enveloping sector of a parabola.

It receives all the luminous flux transmitted by the peripheral lens.Since the lens is itself highly enveloping, a large fraction of theemitted flux thus passes through the lens to be reflected, by thereflector, in the form of rays that are almost parallel.

Only the light rays emitted within the solid angle represented by thesource and the rear edge of the lens are directed to the rear withoutbeing recovered. In general, those rays avoid the optical system formedby the peripheral lens and have a random orientation. The corresponding,frontal part for the solid angle defined by the frontal edge of theperipheral lens, and the vertex of which is the light source, is emitteddirectly.

According to an advantageous feature, the forward opening of theperipheral lens is occupied by a lens whose focal point corresponds tothe light source, so that that lens emits a beam of rays that areparallel to the axis of emission XX. That luminous flux is added to theluminous flux returned by the reflector.

In that manner, almost all of the luminous flux of the source isrecovered in the form of a beam of parallel rays, that is to say, inpractice, of rays that are very slightly divergent. The solid angles ofemission γ and δ are totally controlled. Only the rear angle of emissionβ corresponds to flux of which a portion will be absorbed.

In an advantageous manner, the peripheral lens and the frontal lens areproduced in a single piece or constitute a single piece by the assemblyof two lenses produced separately. The reflector is preferably made ofglossy polished aluminium or of vacuum metallised plastics material, orof glass with reflective dichroic metallisation with, for example,titanium oxide.

According to another feature of the invention, the reflector isgenerated by an arc of an ellipse whose second focal point is located onthe axis of emission.

The invention relates also to a lighting installation composed of aspotlight as defined above and of at least one mirror forming a lightingsystem having an offset focal point, for illuminating an area forillumination that the spotlight cannot reach directly.

Under such conditions, the spotlight can be installed in a location thatis readily accessible; that area can also be accessible on account ofthe power supply that exists in the location or that is easily broughtto the location, without requiring the complex installation in certaincases of cables such as for illumination with a direct spotlight.

Thanks to the very precise pencil of rays formed by the spotlight, it issimple to aim at a deflection mirror, even such a mirror located at arelatively great distance from the spotlight, without giving rise to theconsiderable loss of luminous flux passing to the side of the mirror orwithout requiring a large-sized returning mirror. On the contrary, it ispossible to use mirrors which are small in size, are light-weight andare simple to produce and install.

Since the mirror is generally turned with its reflecting face downwards,there is no risk of its reflecting surface becoming covered with dust ordeposits, so that it requires virtually no maintenance.

According to a particularly interesting feature, the mirror is formed bya plate forming the reflector, which plate is fixed to a sleeveconnected by means of a deformable rod to a foot.

According to another particularly interesting feature, the mirror isformed by a support carrying along its outer periphery a reflector heldin its centre by means of an adjustable screw that is connected to thesupport and adjusts the curvature of the reflector.

The present invention will be described in greater detail below with theaid of the attached drawings, in which:

FIG. 1 is a skeleton diagram of a known spotlight having a parabolicreflector,

FIG. 1A is a graph showing the distribution of the luminous intensity ofa known spotlight according to FIG. 1,

FIG. 2 is a skeleton diagram of a spotlight according to the invention,

FIG. 3 is a more complete view of an embodiment of a spotlight, at thelevel of the lenses,

FIG. 4 is an overall diagram of a spotlight,

FIG. 5 is an axial cutaway view of a first element of the spotlight,

FIG. 6 is an axial cutaway view of the spotlight element equipped withits lamp socket,

FIG. 7 is a diagram of a lighting installation having an offset focalpoint according to a first embodiment,

FIG. 8 is a diagram of a lighting installation having a plurality ofoffset spotlights and a plurality of mirrors according to the invention,

FIGS. 9, 9A, 10 and 10A are enlarged side views and detailed views,respectively, of two embodiments of mirrors according to the invention,

FIG. 11 shows a detail of a mirror fixing,

FIG. 12 is a front view of a mirror according to the invention,

FIGS. 13 and 14 are cutaway views of two other types of mirror accordingto the invention,

FIG. 15 is a cutaway view of a mirror of adjustable curvature,

FIG. 16 shows a system having a plurality of mirrors,

FIG. 17 shows several forms of mirror,

FIG. 18 is a diagrammatic view of a plurality of mirrors supplied by asingle spotlight,

FIG. 19 shows an assembly of a plurality of mirrors,

FIG. 20 is a perspective view of a single mirror of rectangular shape,

FIG. 21 is a perspective view of a single mirror of octagonal shape,

FIG. 22 is a cutaway view of the installation of a mirror according toFIG. 20 or 21,

FIG. 23 is a cutaway view of the installation of a plurality of mirrorsof the type of FIGS. 20 and 21.

A spotlight according to the invention will be described below with theaid of the diagram of FIG. 2.

The spotlight is intended to emit a narrow beam. It comprises a lightsource S which is housed in a bulb (not shown) and is consideredeffectively to be a point source.

The source S, situated on the axis of emission XX, that is to say theaxis along which the beam is to be directed, emits in the solid anglesurrounding it.

In order to simplify the drawing and the explanations, FIG. 2 shows onlypart of an axial section, or supposed axial section, of the spotlightthrough a plane passing through the axis of emission XX.

The source S is bordered on one side of the half-plane delimited by theaxis of emission XX by a convergent lens LA, shown only in section. Thelens has a focal distance that is greater than the distance (d)separating it from the source S, in order to produce a virtual image S′of the source S, which virtual image is situated in the half-plane otherthan that of the lens LA, relative to the axis of emission XX.

Beyond the lens LA there is a concave reflector R defined by a conicsection (ab) of which one or the focal point F coincides with thevirtual image S′ of the light source S. The length of the section (ab)is chosen to cover the entirety of the beam that is emitted by thesource S and has passed through the lens LA.

According to the properties of conics, the rays r1, r2 and all theintermediate rays, reflected by the reflector RF and coming from thesource S, are directed towards the second focal point of the conic,which may be the second focal point of the ellipse located on the axisof emission XX or the focal point shifted to infinity in the directionof the axis of emission XX if the conic section (ab) belongs to aparabola of axis X₁X₁ and of focal point F.

In order also to recover the rays emitted by the solid angle δcorresponding to the cone resting on the edge LA2 of the lens LA andwhose vertex is the source S, there is provided a convergent frontallens LF which is located against the edge LA1 of the lens LA and thefocal point of which coincides with the source S. The lens LF will thenemit rays r3, r4 that are parallel to the axis XX.

In that manner, all the rays emitted by the source S in the peripheralangle γ and the frontal angle δ will be transformed into rays that areparallel or substantially parallel to the axis XX.

In general, the lens LA, of which a segment is shown in FIG. 2 in theform of a section of the lens through a plane resting on the axis XX, isa lens of revolution of axis XX. Under those conditions, the conicsection (ab) also defines a surface generated by the rotation of thesection (ab) about the axis XX (and not the axis X₁X₁). Under suchconditions there is not a paraboloid but a pseudo-paraboloid.

FIG. 3 is a diagrammatic view of a spotlight according to the inventionshowing the monobloc form of a combined lens 1 combining the annularlens LA and the frontal lens LF.

Only the filament constituting the source F of the bulb has been shown.This figure also shows the reflector 3 and the outline of the casing 6of the spotlight.

This figure corresponds to a spotlight having a form of revolution aboutthe axis of emission XX. The various angles of emission γ, δ have beenshown, as has the angle of emission towards the rear β.

FIG. 4 is an axial cutaway view of a practical embodiment of a spotlightaccording to the invention comprising a lens 1 housing a halogen bulb 2inside the reflector 3 carried by a ring 31 equipped with resilienttongues 32 which enter the annular throat 11 of the lens 1. Thereflector 3 is also fixed to the ring 31 by its turned-in base 33,optionally crimped according to a peripheral crown 34 (FIG. 5) in aperipheral throat 35 of the ring 31. The assembly formed by the lens 1,the bulb 2 and the reflector 3 constitutes a product that ismanufactured as such and cannot be dismantled.

FIG. 4 also shows the particular form of the frontal lens, which is infact composed of an annular portion 12 and an axial portion 13 in orderto form a housing 14 that receives the tip 21 of the bulb 2 in the casewhere the lens is separate from the bulb forming the lamp, the body ofthe bulb itself being housed in the cavity 15 defined principally by theinner contour of the annular lens. The assembly so produced can becompleted to the rear by a centring lamp socket 40 in which there engagethe pins 22 of the bulb 2. The lamp socket is itself integrated in aseal 41 through which the contact pins 42 pass. The contact pins areintended to be accommodated in the contact block 5, which is itselfconnected to the power supply.

The assembly described above is housed in a casing 6 of the spotlightwhich is connected in an orientable manner to a foot 7; rotationallocking is effected with the aid of a screw 61 which presses against theouter contour of the joining piece 71 of the foot 7. The otherinstallation means for the spotlight are not shown.

FIG. 5 shows the sub-assembly formed by the lens 1, the bulb 2, thereflector 3 and the ring 31.

FIG. 6 shows the complete sub-assembly formed by a sub-assemblyanalogous to that of FIG. 5, completed by the lamp socket 40 and thebase 41 with the pins 42 passing through.

FIG. 7 shows diagrammatically a first embodiment of a lightinginstallation having an offset light source (or light focal point)according to the invention. The installation is intended to illuminatean object or a surface SE in a very limited and precise manner. To thatend, a spotlight P forming the light focal point according to theinvention is installed close to a power supply A at a readily accessibleheight H. The installation also comprises a mirror M, which isorientable, towards which the beam F of angle α is directed; the mirror,oriented in the appropriate manner, sends back a beam of angle α1 toilluminate the surface SE. The angle α1 is equal to the angle α if themirror M is plane. Otherwise, the angle is different. It may be greaterthan or less than the angle α according to the curvature of the mirrorM.

FIG. 8 is a plan view of an installation having a plurality ofspotlights P1-P6 and a plurality of associated mirrors M1-M6, one mirrorbeing associated with each spotlight. The beams reflected by the mirrorsM1-M6 bear the references α1-α6.

This figure shows one of the advantages of the lighting installationhaving offset source(s) according to the invention, because it allowsthe spotlight to be grouped, for example, in two groups, one containingspotlights P1, P2, P3 and the other containing spotlights P4, P5, P6.The mirrors can be positioned anywhere within the space, so as to be asunobtrusive as possible and to permit the best illumination of thesurface to be illuminated; the latter is not shown in this figure. Thesurface to be illuminated can be composed of a plurality of elementseach illuminated separately by one mirror.

As will be seen hereinbelow, the important factor with regard to themirrors is that they should be as light-weight, unobtrusive andorientable as possible so that they can be installed simply andunobtrusively in the most appropriate locations.

Various examples of mirrors will be described below.

Accordingly, FIGS. 9, 9A show a first embodiment of a mirror 100 formedby a convex reflecting surface 101 that is fixed in its centre to asleeve 102 by means of a screw 103. The sleeve is itself fixed to adeformable rod 104 carried by a tube 105 that is fixed to a foot 106.The foot 106 has, for example, on its rear face, a mechanical fastener107 or two adhesive pads 108 as is shown in FIG. 11. The connectionbetween the sleeve 102 and the deformable rod 104 is made, for example,with the aid of a screw 109 carried by a manoeuvring rod 110. The screw109 compresses the end of the rod 104, which may be a power cablerigidly connected to a conductor, for example of 1.5 mm or 2.5 mm insection, which has the advantage of being very readily deformable and ofretaining the deformation.

The reflecting surface 101 of the mirror is made with the aid of the rod110, which is held in the hand and manoeuvred in order to direct thereflected luminous beam.

FIG. 9A shows the detail of the assembly between the sleeve 102, thereflector 101 with the central screw 103, the end of the rod 104, andthe screw 109 carried by the end of the manoeuvring rod 110. In thisembodiment, the end of the rod 104 is introduced transversely into thehousing of the sleeve 102, and the screw 109 is screwed in the axialdirection.

The variant of the mirror 200 according to FIG. 10 correspondssubstantially to the embodiment of FIGS. 9, 9A except that thedeformable rod 204 enters the sleeve 202 along the axis, and the screw209 is screwed radially. The other elements forming that mirror areanalogous to, if not identical with, those of the mirror 100 and bearthe same reference numerals increased by 100.

Unlike the mirror 100, the mirror 200 does not have a tube 105, and theflexible or deformable rod 204 connects the sleeve 202 to the plate 206.The element 205 fixing the deformable rod 204 to the plate 206 can beconstructed analogously to the element 202. The element 205 can be fixedto the plate 206 from behind with the aid of a screw, and the rod 204can be fixed thereto, as in the sleeve 202, by means of a screw (notshown).

The means for fixing the plate 206 to the support (wall, ceiling orobject) are the same as those for fixing the plate 106 shown in FIG. 11.

FIG. 12 shows a front view of a mirror 250 with an irregular contour 251surrounding the surface 252 of the reflector. The reflector has acentral fastener 253 in the form of a screw. The irregular contour 251is intended to conceal the mirror or integrate it in an assembly.

FIG. 13 is a cutaway view of a mirror 260 of which there are shown onlythe support 261, which carries the reflector 262 in the form of asandwich structure, as well as the deformable rod 263 for orienting themirror.

FIG. 14 shows, in a cutaway view, another form of mirror 270 having asupport 271 in the form of a sleeve which is connected to the deformablesupport rod 273. The actual reflector 272 is surrounded by a frame, forexample a U-shaped profile, 274.

FIG. 15 shows a mirror 280 of adjustable curvature. The mirror iscomposed of a sleeve 281 carrying a support 282 which forms theunderframe of the reflector and carries the reflector 283 along itsouter periphery. In its centre, the reflector 283 is held by a screw 284lodged in a threaded portion of the sleeve 281. By tightening the screwmore or less, the reflecting surface 283 is bent more or less from theplane or almost plane shape shown by the broken line. The sleeve 281 isalso carried by a deformable rod 285.

FIG. 16 shows a system formed by three mirrors 290, 291, 292 which areintended for three separate spotlights or to receive the single beamfrom the same spotlight but deflect parts of the beam in differentdirections. Those reflectors 290, 291, 292 are connected by means ofdeformable rods 293, 294, 295 to a common support plate 296 providedwith fixing means (not shown).

FIG. 17 shows three forms of reflectors 300, 301, 302 which are,respectively, circular, rectangular with rounded corners, and octagonal.Those reflectors can be used to equip the mirrors described above.

FIG. 18 shows an assembly of three mirrors 350, 351, 352 receiving acommon beam and returning parts of that beam in three differentdirections, as is shown by broken lines. The mirrors 350, 351, 352 arecarried by deformable rods 353, 354, 355 on a curved support 356 whichis fixed to a curved support such as a panel 357. Such an installationcan be produced according to any desired orientation on a vertical,horizontal or inclined support 257.

FIG. 19 shows a support rail 360 carrying four mirrors 361, 362, 363,364 which are fixed in an adjustable manner to the rail, which is itselfprovided with fixing means 365, 366. The rail 360 may be a simplestraight rod or a frame 367 such as that shown completely by the brokenline.

FIG. 20 shows a perspective view of a particularly interestingembodiment of a mirror 400 which is formed by a reflector 401 and asupport 402 connected to the reflector by a leg 403. The assembly may becut from a metal sheet and bent as shown.

Because the bent parts are not rigid, it is possible to deform theconnection 403 once the tab 402 has been fixed in the appropriatelocation, in order to orient the reflector 401 as desired.

FIG. 21 shows a reflector 410 which is analogous to the reflector 400 ofFIG. 20 except that it is octagonal and not rectangular in shape.

FIG. 22 is a cutaway view of the reflector 400 showing its fixing to asupport 404.

FIG. 23 is a diagrammatic side view of an assembly of three reflectors420, 421, 422 of the type of FIG. 20, which assembly is fixed to acommon support 423 that is itself fixed to a ceiling, a wall or the like424.

According to a variant which is not shown, some or all of the lenses ofthe spotlight are Fresnel lenses.

What is claimed is:
 1. Illuminating spotlight emitting a narrow beam,comprising a highly concentrated light source and a concave reflectorfor emitting an illuminating beam in a given direction, along an axis ofemission characterised by a convergent lens positioned between thesource and the reflector, and in a plane passing through the axis ofemission: the concave reflector is being defined locally by a conicsection, the source is being bordered laterally on the side of thereflector by a sector of the convergent lens giving a virtual image ofthe source, which virtual image is situated beyond the axis of emission,on the other side from the lens, the virtual image of the light sourcebeing formed at the focal point of the conic section locally definingthe reflector.
 2. Spotlight according to claim 1, characterised in that,the spotlight comprises a body of revolution about the axis of emission(XX).
 3. Spotlight according to claim 1, characterised in that the conicsection is an ellipse whose second focal point is located on the axis ofemission.
 4. Spotlight according to claim 1, characterised in that theconic section is a parabola whose axis is parallel to the axis ofemission.
 5. Spotlight according to claim 2, characterised in that thefrontal opening left by the body of revolution (LA) around the axis ofemission (XX) is occupied by a convergent lens (LF) whose focal pointcorresponds to the light source (S).
 6. Spotlight according to claim 2,characterised in that the lens is in a single piece and houses the lampforming the light source.
 7. Spotlight according to claim 1,characterised in that the angle of coverage (γ) of the peripheral lenscorresponds to the length of the conic section defining the reflector.8. Lighting installation having an offset light focal point,characterised by a narrow beam emitting spotlight, comprising a highlyconcentrated light source and a concave reflector for emitting anilluminating beam in a given direction, along an axis of emission andhaving a convergent lens positioned between the source and thereflector, and in a plane passing through the axis of emission: theconcave reflector being defined locally by a conic section, the sourcebeing bordered laterally on the side of the reflector by a sector of theconvergent lens giving a virtual image of the source, which virtualimage is situated the concave reflector being defined locally by a conicsection, the source being bordered laterally on the side of thereflector by a sector of the convergent lens giving a virtual image ofthe source, which virtual image is situated beyond the axis of emission,on the other side from the lens, the virtual image of the light sourcebeing formed at the focal point of the conic section locally definingthe reflector, and at least one mirror located in the axis of emissionand directing the light towards die surface to be illuminated. 9.Lighting installation according to claim 8, characterised in that themirror (100) is formed by a plate (101) forming the reflector, whichplate is fixed to a sleeve (102) that is connected by a deformable rod(104) to a foot (106).
 10. Lighting installation according to claim 8,characterised in that the mirror (280) is formed by a support (282)carrying along its outer periphery a reflector (283) held in its centreby an adjustable screw (284) that is connected to the support andadjusts the curvature of the reflector (283).